DE60008241T2 - METHOD AND DEVICE FOR EPITACTICALLY GROWING A MATERIAL ON A SUBSTRATE - Google Patents

Abstract

A method of epitaxially growing a material on a substrate (1). The method comprises separately heating precursors to their respective decomposition temperatures at or adjacent a region of the substrate to generate species which are supplied separately to the region and which combine at the region.

Description

The invention relates to a Method and apparatus for epitaxially growing a material on a substrate.

Conventional methods use in typical case an epitaxial reactor with metal-organic chemical Vapor phase deposition (MOCVD). In such a reactor the forerunners, which contain the elements to be grown, the substrate in the form of a Wafers fed, the one on a wafer carrier resting, which is heated. The heat is transferred to the forerunners, which are split or dissociated into nascent atoms, and these nascent atoms are then combined on the surface of the substrate. In a typical example, the substrate will be trimethyl gallium and ammonia along with hydrogen fed to a gallium nitrite layer to build.

A problem with known reactors is that the forerunner have a gap temperature that is much higher than the ideal growth temperatures. For example, ammonia typically requires temperatures up to 1000 ° C or more to effect an effective cleavage while the ideal growth temperature in the order of magnitude of 650 ° C lies.

The problem with conventional Reactors consist of the wafer carrier placing the substrate on a maintains a relatively constant temperature, who typically chose so will match the ideal growth temperature, i.e. in this case 650 ° C. The forerunners Group V, for example ammonia, are at this temperature only split very ineffectively.

The JP-58125698 and the JP-58140391 describe methods of growing InP on a substrate using gaseous mixtures of precursors and decomposition species. The JP-04074858 and the JP-05335622 describe alternative high vacuum decomposition processes in which the decomposition species of a precursor atmosphere react. There is a problem here in disassembling a precursor at a distant location and then mixing the disassembly species with other precursors and their disassembly species before disassembly. However, problems due to the occurrence of undesirable reactions in the mixture persist, reducing the overall effectiveness of the process.

The EP-A-0683249 describes an apparatus for independently supplying cationic and anionic material gases to a substrate using a rotating substrate holder.

According to a feature of the invention this relates to a method for epitaxially growing a material on a substrate, in which precursors, at least of which have two different decomposition temperatures, separated to their respective decomposition temperature in a region of the substrate or nearby of these are heated to produce species that are separated sequentially fed to the area and which are combined in the area.

In contrast to known methods become the forerunners separated to their respective decomposition temperature in this area or heated adjacent to it. This area forms a growth area in which the species are combined. This way everyone can precursor at its cheapest Cutting temperature (gap temperature) are heated during this Procedure is carried out adjacent to the area, which reduces the risk of that nascent atoms reunite before reaching the substrate surface is.

The generated by the decomposition Forerunner species are highly reactive and quickly form stable products. The probability, that the species are involved in further reactions is one Function of time and concentration. By breaking down the forerunners into nearby of the growth area, the generated species are stimulated to combine at the growth area of the substrate instead of unwanted reaction products to build. The decomposition of the forerunners in close proximity with the growth area decreases the amount of time in which unwanted reactions may occur.

Preferably the species of every precursor fed separately to the area one after the other. The species can be separated the area by movement of the substrate to be fed to the movement of the area opposite the places where a decomposition of the forerunners occurs. Typically, at least one of the precursors is separated from the area as Gas flow supplied.

Preferably, the species can be made up of elements Group III and Group V can be selected. Instead, items can Group IV can be used, for example silicon and carbon.

According to the preferred embodiment becomes one of the forerunners, preferably the one with the lowest decomposition temperature, heated to its gap temperature by heating the substrate. In this preferred embodiment another of the forerunners to its gap temperature at a location adjacent to the area heated. In this way, the substrate can range from 550 ° C to 800 ° C, for example to 650 ° C, be heated while the other precursor its optimal gap temperature, either directly or in the presence a catalyst is heated. This is typically the case Temperature in the range between 400 ° C and 1800 ° C.

According to a second feature of the invention, this relates to a device for epitaxially growing a material on a substrate a chamber having a substrate base and having a first inlet to supply a first precursor and having a second inlet separate from the first inlet and supplying a second precursor, the first and second precursors having different decomposition temperatures, wherein first and second heaters are provided to separately heat the first and second precursors to their respective decomposition temperatures on or near an area of the substrate to produce species that are separately supplied to the area and means are provided to control the Supplying species in combination to the region, and wherein the means for sequentially supplying the species further comprise means which cause relative movement between the substrate base and at least one of the inlets.

Preferably the second inlet in a feed line formed, which is adjacent to the substrate carrier. In this way can be the second precursor in an expedient manner be brought close to the substrate.

The second inlet can be different Take forms, including for example a circular one Hole or the like, but preferably the second inlet formed in the form of an elongated slot.

The second heaters are expediently provided in or adjacent to the slot, although they too could be spaced upstream of the slot.

The feed line typically exists made of a refractory material, for example quartz, made of SiN or alumina during the second inlet preferably defines a jet opening that a Cross dimension of, for example, 2 mm.

Preferably the second defines Inlet an outlet direction for the forerunner which runs at an acute angle to the substrate carrier, because this creates a venturi effect that other gases, like hydrogen, which are supplied from a remote source, under which Line to step through.

The second heater is in the typical case in the form of a heating wire, for example consist of iron, nickel, aluminum, platinum or their alloys can and which is made in particular of platinum-rhodium. The Wire is typically spooled.

In most applications it is he wishes, epitaxial growth on a relatively large area of the substrate expand. This is usually achieved by moving the area over the substrate, for example, by providing means that have a relative movement between the substrate carrier and at least one of the inlets cause.

Furthermore, the invention is not limited to Arrangement of a single area on a single substrate. For example can several feed lines be provided to the same or different precursors to feed the substrate and the leads and substrate support are relative to each other movable to align the lines to the different areas. The supply lines can be arranged so that the precursors are separated and in sequence fed to the area become.

Some examples of procedures and Devices according to the invention are described below in conjunction with the accompanying drawings described. The drawing shows:

1 is a schematic cross section through the device of a first embodiment;

2 is drawn to a larger scale a sectional view of a part of the device according to 1 ;

3 is a view of part of the device according to 1 seen from below;

4 is a schematic sectional view of a device according to a second embodiment;

5 Fig. 3 is a schematic plan view of the second embodiment; and

6 is a schematic plan view of a third embodiment.

The reactor according to 1 has a reaction chamber 4 in which a substrate carrier (susceptor) 3 is provided which has a substrate base (wafer carrier) 2 supported. In 1 is a substrate (wafer) 1 on the substrate base 2 arranged. The substrate carrier 3 can be a graphite block which is heated in the usual way, for example by induction, by infrared radiation or by resistance heating methods.

In a side wall of the reaction chamber 4 is a first entry 6 provided, and a gas deflector is located within the reaction chamber 7 to the precursor gases 5 that about the inlet 6 enter after the wafer 1 to judge.

Across the reaction chamber 4 extends an injector line 9 , which is in the form of a refractory tube, for example made of quartz, and a longitudinal slot 10 has, which forms a beam opening that extends along the substrate base 2 extends over the wafer (cf. 2 ).

A straight wire or coil 11 is inside the slot 10 to form a heating element.

When using it becomes a substrate 1 on the substrate base 2 arranged, and the reaction chamber 4 is closed and then the pressure within the chamber is suitably adjusted, typically in the range between 0.7 and 130 kPa (5 to 1000 torr). Typically, the wafer material is chosen so that the epitaxial growth of the material favors and the wafer material can comprise sapphire, GaN, GaAs, SiC or ZnO.

One or more precursor gases 5 are in the chamber via the inlet 6 introduced. Examples of reactive gases are: trimethyl gallium (for Ga deposition), trimethyl indium (for indium deposition), etc., depending on the required composition of the deposition layer. Such a mixture can also have precursors for semiconductor doping. A gas such as B. hydrogen, the mixture 5 also added to stabilize the radicals generated upon dissociation of the precursor.

The substrate carrier 3 is heated such that the substrate 1 and the substrate base 2 also be heated because they are close to the substrate support 3 and so the substrate 1 heated to a suitable growth temperature, ie to a temperature at which the precursor 5 passing through the inlet 6 occurs in the most effective way. A suitable temperature for the growth of GaN is in the range between 600 ° C and 800 ° C.

A second precursor gas 8th , in this case ammonia, is made via the line 9 fed under pressure so that this gas through the jet slot 10 on the heating wire 11 exits over. The wire 11 is heated to a temperature, typically in the range between 400 ° C and 1800 ° C, that is to say a temperature which is suitable for optimally breaking up ammonia in order to generate N and H radicals. In 2 it is shown that the slot 10 relative to the normal to the substrate 1 is hired so that through the inlet 6 imported gases are caused under the line 9 swipe like this by the arrow 30 is specified, as a result of a Venturi effect.

The precursor gas 5 after reaching the substrate 1 broken up in a conventional manner, and the resulting parts, for example the Ga atoms, combine with nitrogen radicals of the gas 8th to an epitaxial growth of gallium nitrite on the on the substrate 1 initiate.

The wire 11 is preferably made of a catalytic material, such as a platinum-rhodium alloy, and in the case of such an alloy can be heated to a temperature which is typically in the range between 600 ° C and 700 ° C. This can be achieved by electrical resistance heating if the element is in the form of a heating wire. The distance between the wire 11 and the substrate 1 is small, so a maximum amount of the broken product of the precursor 8th with the precursor mix 5 reacts on the substrate surface. This optimal distance is also determined by the flow rate of the mixture 5 affected. Typical conditions for ammonia in the generation of GaN is a distance of approximately 5 mm at a flow rate of 0.35 ms ^-1 .

Spraying the second precursor gas onto the area of the substrate has an advantage in that the jet acts as a gas shield, which is all precursor gas 5 and sweeps away its decomposition products that have not deposited on the substrate. This enables the nitrogen radicals and the hydrogen radicals to reach the substrate surface in larger concentrations since they are not with the precursor gas 5 or whose decomposition products are mixed before they reach the substrate surface. This example therefore creates the possibility that the species of each precursor touch the surface of the substrate separately.

To adjust the area of growth, the substrate base 2 movable on the substrate carrier 3 stored, and he can by means not shown in the by the double-headed arrow 31 indicated directions under the line 9 be moved. This movement allows the species from each precursor to separately reach the substrate surface in any order, without mixing with other precursors or the decomposition species.

This procedure can be repeated to deposit more layers on the wafer and so on to produce a multilayer wafer, the materials of different Contains dimensions, dopings or compositions.

The exhaust gases eventually pass through an outlet 33 out.

One application of the invention is the production of microwave devices and opto-electronic Institutions. These facilities are layered with different ones Materials made that have different electrical properties have. The configuration of these layers determines whether the facility for one Microwave emission or light emission is provided, d. H. for one Field effect transistor or for one Led. To achieve an optimal implementation, the Layers grow, if possible with the most ideal temperature. This temperature depends on the material and the device to be manufactured. The advantage of the present invention is that the growth temperature of the materials is not compromised by the need to use a high temperature Breaking up the forerunner material, for example of ammonia. Advantageously creates the invention the possibility precursor use that would otherwise not be compatible in the gas phase, for example dicyclopentadienyl magnesium, since these would otherwise have low-vapor pressure adducts with Group V species would educate for example from ammonia.

A second example of the present invention is shown in 4 shown. In this case the reaction chamber exists 4 ' from a tubular outer quartz cell 60 with a circular cross-section at the end of a cell block 61 is attached. inner half of the outer cell 60 an inner tubular cell with a substantially square cross-section is arranged. A removable molybdenum base plate 66 sits inside the inner cell 65 , The carrier plate 66 extends across the base of the inner cell 65 , The substrate carrier 3 is equipped with heating means, not shown, on the carrier plate 66 rest. There is also a self-supporting gas deflector 7 ' on the carrier plate 66 arranged. A vent 67 for the gases runs through the end of the cell block 61 ,

The injector line 9 enters the cell through the end of the cell block 61 a, and contrary to that in 1 illustrated embodiment, this is in a direction approximately parallel to that of the main gas flow (indicated by an arrow 68 in 4 ) and only extends over half of the substrate 1 , An elongated slot 10 and a heating element 11 suitable dimensions cause deposition in a region between the outer edge and the center of the substrate. In this case, the substrate base 2 within a recess 70 arranged in the substrate carrier 3 is available. The substrate base itself also contains a recess 71 in which the substrate 1 is arranged at the deposit. The dimensions of both recesses and the substrate are such that the outer surfaces of the substrate 1 and the substrate support 2 essentially with the substrate support 3 aligned. The substrate carrier is on a shaft 75 mounted, which enters the cell from below and through holes in the substrate carrier 3 the carrier plate 66 and the cell walls 60 . 65 runs. The cell walls 60 . 65 are equipped with suitable gas seals to keep the cell leak-tight. The lower end of the shaft is on a motor 80 or another suitable rotary drive.

In operation, both the outer and inner cells are evacuated to the pressure differential across the inner cell walls 65 to reduce. As in the previously described embodiment, one or more precursor gases enter the inner cells from the inlet on the right side as shown in the drawing (not shown). The material is deposited in a similar manner. However, this causes the shaft to rotate 75 by the engine (by the arrow 76 in 4 shown) a relative rotary movement instead of a reciprocating movement with respect to the injector line.

In this example there are injector lines 9 and wave 75 detachable from the device so that the support plate 66 , the gas deflector 7 ' and the substrate support structure can be removed by sliding.

5 shows an apparatus for growing materials on multiple substrates 17 on a heated susceptor 18 are arranged in a chamber, not shown. One line or both lines 19 and the susceptor 18 are rotatable. Layers of a semiconductor substrate can be processed in succession using multiple precursor feed lines 19 according to the line 9 are deposited, which run radially from the center of the susceuptor. According to one embodiment, the feed lines are grouped as shown such that they combine precursors for both reaction species simultaneously in a single area. The substrates 17 are successively in the immediate vicinity of the feed lines 19 by relative movement between lines 19 and substrates 17 brought. In this case, hydrogen, nitrogen, argon or another suitable cleaning gas is introduced into the system in the middle of the substrate carrier, which flows radially outwards instead of being supplied directly with one of the precursors. This flow sweeps away the consumed reaction products.

According to a modified embodiment 6 lead lines 19a and 19b individually precursors to the growth area one after the other and a rapid relative movement between each substrate and each precursor line ensures that there is only a short time between the release of the species. The effectiveness of the deposition process is therefore improved, since in any case the species from the precursors can reach the substrate without reacting with the species of the other precursors or with the precursors themselves.

The lines 19a and 19b lead the forerunners from the circumference of an annular susceptor. The substrates are arranged in the circumferential direction over the surface of the circular susceptor. It is clear that one or more of the lines are provided with means to disassemble one or more of the supplied precursors.

In this example, each line is equipped with heating wires to disassemble the separate precursors at their respective temperatures. The lines 19a lead to a precursor of group V, namely ammonia, and the lines 19b lead to a precursor of group III, namely trimethyl gallium. The substrates 17 are also heated by methods similar to those of the previous examples, and the heating ensures the uniformity of the deposited materials.

This arrangement is particularly advantageous in that the device can be set up to manufacture devices in large quantities without changing the gas flow or chemistry in the vicinity of each substrate. This can be done by changing the radius of the circular susceptor 18 is increased, thereby creating the possibility that multiple substrates can be arranged around the circumference, together with multiple lines 19a and 19b how this seems appropriate in each case. In addition, substrates of different sizes can be used.

Although in 6 Not shown, a radial flow of hydrogen can be supplied in this example. Instead, other gases such as nitrogen or argon can be used.

Claims (27)

Method for epitaxially growing a material on a substrate ( 1 ) with which forerunner ( 5 . 8th ), at least two of which have different decomposition temperatures, separately heated to their respective decomposition temperatures in or near an area of the substrate to produce species which are separately sequentially fed to the area and which are combined in the area. A method according to claims 1 or 2, in which the species separated the area by relative movement of the substrate supplied to cause the area to move relative to those locations on which the decomposition of the forerunners occurs. Method according to one of the preceding claims, which separated at least one precursor supplied to the area as a gas stream becomes. The method of claim 3, wherein the gas stream arranged to provide gas shielding to precursors or To dissect cutting products, that do not adhere to the substrate. Method according to one of the preceding claims, which is the species from group III and group V of the periodic System of elements selected are. Method according to one of claims 1 to 4, wherein the Species are selected from Group IV of the elements. The method of claim 5, wherein the species Are gallium and nitrogen. The method of claim 6, wherein the species Are carbon and silicon. The method of claim 7, wherein one of the precursor Is ammonia. Method according to one of the preceding claims, which the substrate is a semiconductor, for example gallium arsenide, is. Method according to one of the preceding claims, which the substrate is a semiconductor, for example silicon carbide, is. Method according to one of the preceding claims, which one of the forerunners heated to its decomposition temperature by heating the substrate becomes. The method of claim 12, wherein the substrate heated to the decomposition temperature of the precursor with the lower decomposition temperature becomes. The method of claim 12 or 13, wherein the substrate is heated to a temperature between 550 and 800 ° C becomes. Method according to one of the preceding claims, which one of the forerunners to its decomposition temperature at a location adjacent to that Area is heated. The method of claim 15, wherein the precursor is a temperature in the range between 400 and 1800 ° C is heated. Method according to one of the preceding claims, which the area over the substrate is moved. Device for epitaxially growing a material on a substrate ( 1 ) with one chamber ( 4 ) that have a substrate base ( 2 ) and has a first inlet ( 6 ) has a first precursor ( 5 ) and the second inlet ( 9 ), which is separate from the first inlet and a second precursor ( 8th ), wherein the first and second precursors have different decomposition temperatures, with first and second heaters being provided to separately heat the first and second precursors to their respective decomposition temperatures on or near a region of the substrate to produce species that separate are supplied to the region, and wherein means are provided to deliver the species in combination to the region, and wherein the means for sequentially supplying the species further include means that cause relative movement between the substrate base and at least one of the inlets. The apparatus of claim 18, wherein the second Inlet in a supply line is provided, which is adjacent to the substrate base. The apparatus of claim 19, wherein the second Inlet has the shape of an elongated slot. Apparatus according to claims 19 or 20, in which the second heating means are arranged in or adjacent to the slot is. Device according to one of claims 18 to 21, wherein the second heating means are in the form of a heating wire. The apparatus of claim 22, wherein the heating wire consists of a catalytic material. Device according to one of claims 18 to 23, wherein the first heating means are arranged at a point in which the Substrate base is heated. The apparatus of claim 18, wherein a plurality of supply lines is provided to same or different precursors by area to feed the substrate, the lines and the substrate base being movable relative to one another to align the lines to different areas. The apparatus of claim 18, wherein the means for consecutive feeding of the species are designed so that a relative movement between causes the substrate base and at least one of the inlets in the transverse direction becomes. The apparatus of claim 18, wherein the means for successive feeding of the species are designed in such a way that a relative movement between causes the substrate base and at least one of the inlets in the direction of rotation becomes.